Projectile

ABSTRACT

Projectile for a small arms weapon having a barrel. The projectile comprises a projectile body; a plurality of external peripheral fins; a coupling for each fin to mount the fin to the projectile body to enable pivotal movement of the fin from an un-deployed position to a deployed position and to enable displacement of the fin in a radial direction of the projectile body; and means to bias displacement of the fin in the radial direction.

The present invention relates to a projectile for a small arms weapon having a barrel, such as a shotgun, and in particular a projectile having an improved fin configuration.

Projectiles for a small arms weapon, which have stabilising fins are known in the art. For example, WO 02/090870 describes a known projectile having deployable fins. When such a projectile leaves the barrel of the weapon the external peripheral fins deploy from a radially inward position to a radially outward position to provide stability of the projectile during flight.

In this regard, such finned projectiles are known to offer a high level of accuracy over a given range, which has been attributed to their stability during flight as a result of the fins. However, testing has shown that the improvements in accuracy are not always consistent; with a range of accuracies being exhibited within a particular production batch. Moreover, there is always a need for increased accuracy over a longer range.

Detailed analysis of such projectiles has shown that these variations in accuracies are caused by production tolerances. For instance, the applicant has identified a phenomena of fin wobble during flight. That is, once in the deployed position, the fins wobble or rock slightly at the contact between the fin and the casing. This wobble causes minor deviations in the projectile's flight, which in turn reduces accuracy. Furthermore, aerodynamic analysis has shown that, in some instances, the tips of some of the fins can protrude into turbulent air outside of the clean air flows immediately adjacent the projectile during flight. This affects the stability of the projectile's flight, and hence its accuracy.

In this regard, the applicant has identified that the above problems can be attributed to the contact between the fin relative to the projectile casing. In the fin construction of the aforementioned known projectile, the fins pivot relative to the surface of the projectile casing, until the fin comes into contact with the casing. As such, because the casing is cylindrical, contact between the fin and the casing only occurs along a single strip parallel to the axis of fin rotation; this strip of contact defining the deployment position of the fins. Thus, minor manufacturing tolerances can cause variations in the distance between the pivot point and the edge of the fin, which in turn affects the position where the strip of contact between the fin and the casing is made. This causes very slight positional inaccuracies in the location of the fins once they are deployed. Therefore, as the exact position of the fins cannot be accurately controlled, the stability of the projectile during flight and hence its accuracy is affected. Furthermore, in some instances when the fins are able to pivot too far, their tips may protrude into the turbulent air flow around the projectile and cause more significant variations in accuracy. Indeed, in the worst cases, a fin may even be able to pivot back on itself, which could cause the projectile to become dangerously inaccurate.

The present invention seeks to overcome these problems associated with the prior art and provide a projectile having improved accuracy.

According to an aspect of the present invention there is provided a projectile for a small arms weapon having a barrel, the projectile comprising:—

a projectile body;

a plurality of external peripheral fins pivotable from an un-deployed position to a deployed position;

wherein each fin is formed to have a contact surface for contacting with the projectile body when the fin is moved into the deployed position, said contact surface being configured to fit to the opposing surface of the projectile body to form at least two points of contact that are circumferentially offset about the longitudinal axis of the projectile and thereby provide a position of maximum deployment of the one or more fins.

In this way, the fit between the contact surface and the opposing surface of the projectile body essentially creates a contact by which the fin abuts against the projectile body in a manner such that the fins are much more stable when in a deployed position compared to the point or edge contact formed with the above mentioned prior art projectiles. Not only does this prevent the fins from pivoting beyond their intended deployed position, but also acts to reduce any fin wobble which may result due to manufacturing tolerances. Accordingly, any such manufacturing tolerances have a lessened impact on the position of the fins when in a deployed position and therefore fin position can be better controlled, thereby improving consistency between projectiles from differing batches.

Conveniently, the two points of contact are provided on a single surface.

Conveniently, the contact surface fits to the opposing surface of the projectile body over the entire extent of the contact surface.

In this way, the surfaces fit to one another over an enlarged area, providing improved fin stability.

Conveniently, the contact surface is a substantially flat surface.

Conveniently, the projectile body comprises a flattened abutment surface for each said fin, the flattened abutment surface forming said opposing surface of the projectile body against which fits the contact surface of the respective fin.

In this way, a straightforward match between the surfaces can be achieved with relatively simple manufacturing. Furthermore, the flattened abutment surfaces do not affect the aerodynamic characteristics of the projectile when they are located at the rear thereof, since during flight the air flow at this location is laminar (clean). As such, the flight of the projectile is unaffected by the flattened sections.

Conveniently, the projectile body comprises a cylindrical section and the contact surface of each fin is arcuate with a radius matching that of the cylindrical section to fit thereto.

Conveniently, the contact surface of each fin is provided with recesses.

According to another aspect of the present invention, there is provided a projectile for a small arms weapon having a barrel, said projectile comprising:—a projectile body; a plurality of external peripheral fins; a coupling for each fin to mount the fin to the projectile body to enable pivotal movement of the fin from an un-deployed position to a deployed position and to enable displacement of the fin in a radial direction of the projectile body; and means to bias displacement of the fin in the radial direction.

In this way, the projectile has a variable diameter, enabling it to pass through a choked section of a weapon barrel, whilst forming a good fit with the barrel at the larger diameter sections. Accordingly, accuracy and power are not affected when using the projectile in a choked barrel having a narrowed section.

Conveniently, said coupling comprises:—channel means formed in said fin to be aligned with the axis of said projectile and having a slot shaped cross section with a longer axis facing towards said radial direction; and pin means mounted to the projectile body to locate with said channel means to provide said pivotal movement of the fin.

Conveniently, said channel means extends along the entire length of the fin in the direction of said axis of the projectile.

Conveniently, the pin means comprises a single pin extending along the entire length of the fin in the direction of said axis of the projectile.

Conveniently, pin means comprises a pair of pins, each extending into an opposing end of said channel means.

Conveniently, said coupling comprises:—pin means extending from either end of the fin in the direction of said axis of the projectile; and channel means formed in said projectile body to be aligned with the axis of said projectile and receiving said pin means fin, wherein the channel means has a slot shaped cross section with a longer axis facing towards said radial direction.

The invention will now be described, by way of illustration only, with reference to the accompanying drawings in which:

FIG. 1 is a rearward cross-sectional view of a projectile body of a projectile according to an embodiment of the present invention, wherein fins are partially deployed;

FIG. 2 shows a rearward cross-sectional view of the projectile body and fins shown in FIG. 1 when the fins are un-deployed, along with an enlarged view of the position of the fins;

FIG. 3 shows a rearward cross-sectional view of the projectile body and fins shown in FIG. 1 when the fins are partially deployed, along with an enlarged view of the position of the fins; and

FIG. 4 shows a rearward cross-sectional view of the projectile body and fins shown in FIG. 1 when the fins are fully deployed, along with an enlarged view of the position of the fins.

FIG. 5 is a rearward cross-sectional view of a projectile embodying another aspect of the present invention when the projectile is in a relatively wide diameter section of a weapon barrel, along with an enlarged view of the position of the fins;

FIG. 6 shows a rearward cross-sectional view of the projectile shown in FIG. 5 when the projectile is in a relatively narrow diameter section of a weapon barrel, along with an enlarged view of the position of the fins;

FIG. 7 shows a rearward cross-sectional view of the projectile shown in FIG. 5 when the fins are deployed, along with an enlarged view of the position of the fins.

FIG. 1 illustrates a view towards the rear, in cross section, of a projectile taken near the rear end thereof with parts other than the projectile body and fins omitted for the sake of clarity. The drawing shows a projectile body comprising a longitudinal casing, with a front section (not shown) which contains an explosive payload (also not shown), and a rear section 3 which supports four fins 2. The overall construction is similar to that described in the applicant=s earlier applications WO 02/090870 and WO 02/084205. That is to say, the projectile body and fins shown in FIG. 1 are incorporated into a projectile such as that described in these applications. The fins 2 are mounted to the rear section to pivot around pins 4, which are located between opposing lugs 7. It will be seen therefore that the cross section is taken through the fins between the opposing lugs 7. The fins 2 are disposed equidistantly around the circumference of the projectile body.

In FIG. 1, for clarity, the fins 2 are shown in a partially deployed position. The fins 2 are provided with a profile which helps stability during flight (not shown). A fin deployment mechanism (not shown) is used to move the fins 2 into a deployed position once a projectile incorporating the projectile body and fins has left the barrel of a weapon. Such fin deployment mechanisms are described in the applicant=s own earlier patent applications WO 02/090870 and WO 02/084205. In the present embodiment the fin deployment mechanism comprises a torsion spring (not shown) for each of the fins 2 which acts to bias the fins 2 to pivot towards the deployed position (as shown in FIG. 4), although alternative fin deployment mechanism could also be used, for example using air pressure or actuating pins to open the fins.

As can be seen in FIG. 1, the rear section 3 of the projectile body is not entirely cylindrical and comprises four opposing surfaces, one for each fin, which take the form of flattened abutment areas 5 adjacent to and spaced from the pins 4 of each of the fins 2. At the same time, the fins 2 are provided with flattened contact surfaces 6 at their ends closest to the pins 4. The abutment areas 5 and flattened contact surfaces 6 are configured so as to fit to each other. This is described in further detail below.

The operation of the present invention will now be described with reference to FIGS. 2 to 4.

When the projectile is first loaded into the barrel, it is provided inside a cartridge sleeve which also contains the propellant charge. In this state the fins 2 are in an un-deployed position and are retained in this position by the cartridge sleeve. When the propellant charge is detonated, the projectile is forced out of the cartridge sleeve and along the barrel of the weapon. The barrel also acts to retain the fins 2 in the un-deployed position.

FIG. 2 shows the rear section 3 of the projectile body with the fins 2 in an un-deployed position. In this position, the fins 2 are folded down against the rear section 3 of the casing and held in place by either the cartridge sleeve or the barrel of the weapon as described above.

When the projectile exits the barrel, the fins 2, by action of the springs, pivot outwardly to a deployed position as the barrel is no longer present to restrain them. FIG. 3 shows a similar view to FIG. 2 but shows the location of the fins 2 shortly after the projectile has emerged from the barrel, where the fins 2 are in a partially deployed position, similar to the view shown in FIG. 1. As shown in the enlarged view, as the fins continue to pivot towards the deployed position, the contact surface 6 of fin 2 moves towards the flattened abutment area 5 provided on the rear section 3.

FIG. 4 shows the rear section 3 of the projectile body with the fins fully deployed. As can be seen in the enlarged view, in this position, the entire contact surface 6 has moved to fit against abutment area 5, and the springs act to hold the fins in this position against the abutment surface. The matching of these two surfaces maintains stable positioning of the fins once deployed and prevents the fins from pivoting beyond their intended deployed position, thereby providing much better control of the fin position.

In the present embodiment, flattened abutment areas 5 are provided on the rear section 3 of the projectile body which allows the corresponding flattened contact surface 6 of the fin to fit to it. That is, an enlarged area of contact is provided between the fin and the projectile body when the fin is in the deployed position, creating two or more contact points (in this case multiple points represented by the entire extent of the surface 6) that are circumferentially offset about the longitudinal axis of the projectile body (i.e. they are at different positions within a plane perpendicular to the axis of fin rotation). Therefore in this embodiment, the contact points are formed along the entire length of the contacting area in a direction of a chord about the axis of the projectile body.

This construction provides the fins with significantly greater stability when in the deployed position. As such, the fin is prevented from wobbling by being braced over a larger area. Moreover, this construction also means that any minor manufacturing tolerances have a lessened impact on the position of the fins when in a deployed position. For example, the fins are unable to pivot beyond the predetermined position of maximum deployment since there is a contacting area over which the fin abuts against the casing.

Accordingly, the present invention provides a projectile having improved fin stability during flight and, hence, improved accuracy.

It will be understood that the illustrated embodiment described herein shows an application of the invention in one form only for the purposes of illustration. In practice the invention may be applied to many different configurations the detailed embodiments being straightforward to those skilled in the art to implement.

For example, the contact surface 6 and abutment surface 5 may not necessarily be flat, provided that they fit to one another to produce at least two contact points at different positions circumferentially offset about the longitudinal axis of the projectile. For instance, the abutment surface may be cylindrical, provided that the contact surface of the fin has an cylindrical configuration so that the two surfaces are able to fit to one another. Furthermore the contact surface and abutment surface may include surface formations which engage or match with one another. Similarly, the contact surface and abutment surface need not necessarily fit to one another along their entire extent of the surfaces thereof, provided they provide contact at two or more points at different positions perpendicular to the axis of fin rotation thereby forming two or more contact points.

FIG. 5 illustrates another aspect of the invention and is a view towards the rear, in cross section, of a projectile taken near the rear end thereof with parts other than the projectile bod and fins omitted for the sake of clarity.

The drawing shows a projectile body comprising a longitudinal casing, with a front section (not shown) which contains an explosive payload (also not shown), and a rear section 3 which supports four fins 2. The overall construction is similar to that described in the applicants earlier applications WO 02/090870 and WO 02/084205. That is to say, the projectile body and fins shown in FIG. 5 are incorporated into a projectile such as that described in these applications. The fins 2 are mounted to the rear section to pivot around pins 4, which are located between opposing lugs (not shown for clarity). It will be seen therefore that the cross section is taken through the fins between the opposing lugs 7. The fins 2 are disposed equidistantly around the circumference of the projectile body.

The fins 2 are provided with a profile which helps stability during flight (not shown). A fin deployment mechanism is used to move the fins 2 into a deployed position once a projectile incorporating the projectile body and fins has left the barrel of a weapon. Such fin deployment mechanisms are described in the applicants own earlier patent applications WO 02/090870 and WO 02/084205. In the present embodiment the fin deployment mechanism comprises a torsion spring 6 for each of the fins 2 which acts to bias the fins 2 to pivot towards the deployed position (as shown in FIG. 7), although alternative fin deployment mechanism could also be used, for example using air pressure or actuating pins to open the fins.

In contrast to the projectiles of the applicant's own earlier patent applications, with the present invention, the pins 4 are received in elongate channels 5, which are formed in the fins 2, and which have an elongate or elliptical slot shape in cross section. In this respect, when the fins are in the undeployed position as shown in FIG. 5, the longer axis of the ellipse is substantially aligned with a radius of the projectile.

Thus, the fins 2 can move with respect to the pins 4 in a radial direction relative to the projectile when the fins 2 are in the undeployed position. In this connection, the spring 6 acts between the surface of the rear section 3 of the projectile casing and the fin 2 to pivot the fin outwardly to deploy when the projectile exits the barrel. When the projectile is travelling inside the barrel of the weapon, the walls of the barrel act to hold the fins in the undeployed position. In doing this, the longer axis of each channel 5 in cross section is aligned with the radial direction of the projectile.

As the ends of the fins 2 are held next to the rear section 3 by the barrel, the springs 6 urge the fins 2 radially outward. In the configuration shown in FIG. 5, where the projectile is travelling in that part of the barrel of the weapon with the greatest diameter, each channel 5 is dimensioned and orientated in cross section so that the corresponding pin 4 abuts the inner surface 5 i of the channel 5 which is radially closest to the projectile. Therefore, the effective diameter of the projectile is at a maximum.

As the projectile moves along the barrel and reaches a choked section having a narrower diameter, as shown in FIG. 6, the fins are forced radially inwardly against the resilience of the springs. This causes the pins 4 to slide within the slot shaped cross section of the channel (i.e. perpendicular to the length of the channel itself) towards the outer edge 5 o of the slot shape as shown. The movement of the fins radially inwardly results in an overall reduction in the diameter of the projectile. This reduction in diameter allows the projectile to pass through the choked section of the barrel without damaging the fins or any other component of the projectile or the barrel itself.

FIG. 7 shows the projectile when the projectile has left the barrel. In this position, the fins are deployed under the action of the springs 6. In this regard, when the projectile emerges from the barrel, the fins are no longer restrained by the barrel and as each fin pivots about its respective pin, the corresponding pin 4 slides in the channel (perpendicularly to the length of the channel) to move towards and abut the inner surface 5 i of the channel which is radially closest to the projectile, similar to that shown in FIG. 5. At the same time, the fins 2 pivot about the pins 4 until the projectile is in the configuration shown in FIG. 7. In this way, the fins move eccentrically about the longitudinal axis of the projectile.

It will be understood that the illustrated embodiment described herein shows an application of the invention in one form only for the purposes of illustration. In practice the invention may be applied to many different configurations the detailed embodiments being straightforward to those skilled in the art to implement. For instance, in the above examples, springs 6 have been used as the fin deployment means. However other fin deployment mechanisms, such as fin engagement pins and associated mechanisms, could alternatively be used. Suitable fin deployment mechanisms are described in the Applicant=s own earlier applications WO 02/090870 and WO 02/084205.

Furthermore, it will be understood that the combination of pins 4 and channels 5 can be varied to provide the radial movement of the pins whilst traveling along a weapon barrel with variations in diameter thereof. In this connection, the total change in diameter of the projectile when the fins are in the un-deployed state, that is the tolerance of the projectile to pass through a narrowing in the barrel, is determined by the size of the elongated cross section of the channel relative to the size of the pin. Where fins are provided around the circumference of the casing at diametrically opposed positions, as shown in the above examples, the total difference in diameter achieved is double the size of the elongation of a single slot shape cross section of the channel (relative to the cross section of the pin). It is to be realised that the difference in diameter can be altered by changing the relative disposition of the fins about the circumference and/or by changing the size of the cross section of the channels In the illustrated embodiments, four fins are shown. However, the invention is not limited in this respect.

In this connection, in a preferred embodiment, each pin 4 has a diameter of 1 mm and each slot shaped cross section is enlarged or extended by 0.25 mm further. In other words, each slot shaped cross section of a channel has a length of 1.25 mm and a width of 1 mm. In this way, the projectile has a total tolerance of 0.5 mm, which is sufficient to enable the projectile to pass through the choked section of a barrel of most weapons of this type. For example, in one type of weapon, the barrel diameter changes from 17.8 mm to 17.4 mm at the choked section. It will be understood, however, that the sizes of the pins and channels can be varied depending the type of choked barrel with which the projectile is to be used.

Moreover, the present invention need not necessarily restricted to use with choked weapons since the above construction allows the projectile of the present invention to be used with weapons where there are small differences in barrel diameter between them. Thus, the present invention can provide a more universal projectile which can be used with a wide variety of weapons. In this regard, weapons produced by different manufacturers can have minor differences in barrel diameters. This may result in power or accuracy loss when using the weapon with a projectile produced by another manufacturer or intended for another weapon. However, the present invention can accommodate such variations in barrel diameter without losing power or accuracy.

It will be apparent that the pin 4 does not have to extend along the entire length of the channel 5 formed in the fin 2 and can be split into two with a sub pin extending partially into one end of the channel 5 and a sub pin extending partially into the other end of the channel 5. Moreover, the channel 5 does not have to extend along the entire length of the fin 2 or be a closed channel.

Furthermore, whilst the embodiment of FIGS. 5 to 7 shows the pins extending from opposing lugs of the rear section 3 and extending into the channel 5 in the fin, the present invention can encompass pins formed on the fin 2 which extend into channels formed in the lugs, which channels have a slot shape in cross section similar to that shown in FIGS. 5 to 7. 

1. A projectile for a small arms weapon having a barrel, said projectile comprising:— a projectile body; a plurality of external peripheral fins; a coupling for each fin to mount the fin to the projectile body to enable pivotal movement of the fin from an un-deployed position to a deployed position and to enable displacement of the fin in a radial direction of the projectile body; and means to bias displacement of the fin in the radial direction.
 2. The projectile according to claim 1 wherein said coupling comprises:— channel means formed in said fin to be aligned with the axis of said projectile and having a slot shaped cross section with a longer axis facing towards said radial direction; and pin means mounted to the projectile body to locate with said channel means to provide said pivotal movement of the fin.
 3. The projectile according to claim 2 wherein said channel means extends along the entire length of the fin in the direction of said axis of the projectile.
 4. The projectile according to claim 3 wherein the pin means comprises a single pin extending along the entire length of the fin in the direction of said axis of the projectile.
 5. The projectile according to claim 2 wherein the pin means comprises a pair of pins, each extending into an opposing end of said channel means.
 6. The projectile according to claim 1 wherein said coupling comprises:— pin means extending from either end of the fin in the direction of said axis of the projectile; and channel means formed in said projectile body to be aligned with the axis of said projectile and receiving said pin means fin, wherein the channel means has a slot shaped cross section with a longer axis facing towards said radial direction. 